The feasibility of a novel, solid phase, colorimetric assay will be investigated. Monoclonal antibodies will be covalently immobilized on glass as the solid matrix. Several chemical reactions will be studied to identify linkages that give low nonspecific binding of proteins and small molecules while maintaining the integrity of immunoglobulins. Glass will be chemically refined to obtain a uniform, reproducible coat of antibodies independent of the physical history of glass and batch to batch variation. A new conjugate, hapten-biotin, will be evaluated with streptavidin-enzyme as a tracer for colorimetric quantification. The resulting solid phase assay will be implemented initially for measurement of progesterone in milk of cows. It is our intention to develop a simple, relaible assay for monitoring estrous cycle, ovarian cyclicity post partum, ovarian dysfunction, and pregnanacy in dairy cows. A practical procedure to measure progesterone concentration in milk outside a laboratory setting also has substantial economic value in cattle breeding. Phase I of this project will establish the feasibility of such a method while phase II will be devoted to subsequent development of an assay which can be performed under field conditions by a nontrained person.